Telephone system



July 30, 1940. J. bAvmsoN. JR

TELEPHONE SYSTEM Filed July 17, 1937 'snets-sneet 1 E/NI/ENTOR By J. DAV/DSON JR.

July 30, 1940. DAVIDSON. JR

TELEPHONE SYSTEM Filed July 17, 1937 2 Sheets-Sheet 2 K335 wz mwqwk amok SE10 /Nl/EN7'0R By J. DAV/DSONJ/P.

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WEE Eek $85 255% ArmQA/EK Patented July 30, 1940 PTENT DFFEQ TELEPHONE SYSTEM John Davidson, Jr., Montclair, N. 3., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 17, 1937, Serial No. 154,231

r 9 Claims.

This invention relates to telephone systems and particularly to special service systems such as intercepting equipments in telephone systems.

An object of the invention is to provide an improved economically arranged ringing, signaling and tripping arrangement for intercepting equipments.

Heretofore systems have been provided in which, when subscribers lines are changed or disconnected, calls for such lines over automatic telephone systems are extended to terminals connected to intercepting trunks leading to intercepting apparatus for supervision by operators.

In such systems in case of an intercepting trunk circuit, for example, extending to a distant office, the ringing is usually tripped by the application of ground on the ring'conductor as the ringing source is usually applied on this conductor. After the tripping relay has operated, the tripping ground connection on the ring conductor should not set up a false charge condition in the connector circuit which might occur should the operating battery connected through the winding of the usual supervisory relay be connected to the ring conductor. This is the usual practice as the operating battery in the preceding switches, such as selectors; is connected to the ring conductor. For operating reasons this is the preferred method. To avoid such'false charge conditions the operating battery in the connectors are sometimes poled differently from the preceding switches. That is, with battery connected to the tip conductor and ground to the ring conductor. t

It is a feature of this invention to provide a tripping arrangement for ringing in systems of this kind which includes cold cathode tubes. With this cathode tube arrangement the tripping relay in the automatic system is operated to trip the ringing as soon as theccnnectiou is established to the terminals of the intercepting trunk circuit. The cold cathode tube operates on the ringing voltage to establish'a ground connection to the trunk conductors. As these tubes will not operate on the ordinary 48-volt operating battery, it cannot set up a false charge condition in the connector by operating the supervisory relay even though battery may be connected through the supervisory relay to the ring" conductor of the line. This invention may be'appli'ed in systems of this kind in a number of difierent ways. For example, the tripping arrangement may be connected in the intercepting trunk to ground to a ring conductor as is the'usual arrangement or to both the tip and'ring conductors to trip ringing on either the tip or the ring conductor during the positive half of the ringing cycle depending on the conductor to which the ringing battery is connected. The system may also be arranged for tripping during both the positive and the negative halves of the ringing cycle by connecting two tubes alternately poled to the tip or ring conductors, or to both conductors. In some in stances a tube may be arranged across the tip and ring conductors of a cord circuit for use by an intercepting operator to trip the ringing when she plugs into an intercepting trunk.

This invention has been illustrated in the accompanying drawingsjin which:

Fig. 1 shows a connector and ass'ociatedterminals of an automatic step-by-step telephone system;

Fig. 2 shows a manual intercepting trunk terminating in the same ofiice and selectable by the connector shown in Fig. 1;

Fig. 3 shows an intercepting trunk terminating in a distant oflice and selectable by the connector of Fig, 1; I

Fig. 4 shows an intercepting operators cord circuit in the same office; and

' Fig. 5 shows a modified form of the applicants invention as applied to an intercepting trunk circuit such as shown in Fig. 3.

Referring now to the drawings, terminals, accessible through a connector C shown in Fig. 1, and that have been disconnected from subscribers lines, may be connected to intercepting trunks so that calls for these subscribers will be taken care of by operators. In Fig. l the terminals I00 and 102 that were normally connected to a two-party subscribers line have been shown connected to an intercepting trunk, shown in'Fig. 3. This trunk terminates in a distant office in a jack 399 in front of an operators position who intercepts calls directed over this trunk. The terminals H2 that were also normally connected to a subscribers line have been shown connected directly to a trunk terminating in a jack in the same ofi'ice so that when calls are directed to these latter terminals the intercepting operator at this oflice may answer by using the intercepting cord circuit shown in Fig. l.

If it is assumed that the last two digits of a called subscribers number cause the connector C to have its brushes land on the terminals Hill, the operations of the connector may be as follows: The connector may be seized by brushes I l3 from a selector connecting with the terminals of this connector and this causes the operation of relay H4 from battery and ground through the winding of this relay, terminals of relay 5 over the tip and ring conductors, then over the selector and other intermediate switches, if any, to the calling subscribers loop. The operation of relay II4 closes an obvious circuit for the operation of relay H6 which is slow in releasing and remains operated during the succeeding dial pulses representing the tens digit. The first release of the pulsing relay H4, when the calling subscriber dialed this digit, closes a circuit for the vertical magnet II'I through the winding of this magnet and relay H8, vertical off-normal contacts and contacts of relays H6 and H4 to ground. This causes the connector to take one vertical step and operate the vertical off-normal contacts. Relay H8 is operated in this circuit and a circuit from now on will extend through contacts of relay H8 and the vertical off-normal contacts, and relay I I8 is maintained operated during the succeeding impulses of this digit. At the end of the tens digit relay H8 releases and on the first release of relay H4 in response to a unit digit the rotary magnet I20 will operate over a circuit from battery through the winding of this magnet, contacts of relays I2I, I22 and I I8, the vertical off-normal contacts, contacts of relays H6 and H4 to ground. This circuit is also completed for relay I23, over contacts of relay I22, which operates and provides a locking circuit for itself independent of contacts of relay I22, and remains operated during the dialing of the unit digit. At the end of the unit digit, the brushes of the connector C land, as assumed, on terminals I00.

If the trunk shown in Fig. 3 is busy, there will be ground on the sleeve conductor and therefore a circuit will be completed immediately before the slow-release relay I23 releases for the operation of relay I22 from battery, through the winding of this relay, contacts of relays I2I and I23 to ground on the sleeve. Relay I22 in operating provides a locking circuit for itself when relay I23 releases through the make-beforebreak contacts of relay I23 and its own contacts to the ground at contacts of relay II6. Relay I22 in operating applies a busy tone from the source I25 over its upper inner armature and front contact to the ring conductor of the connection towards the calling subscribers line.

If, however, the intercepting trunk is idle, a connection is established for the operation of relay I2I on the release of relay I23 from battery through the winding or relay 302, contacts of relay 303, the sleeve circuit, contacts of relay I23, lower winding of relay iZI to ground at relay I I6. Relay I 2| in operating .closes a locking circuit for itself from battery through the upper winding and upper inner armature and front contact to ground at contacts of relay H6, and closes connections for the usual ringing of a called subscriber. In this case the ringing goes out towards the trunk in Fig. 3, from the source I26, contacts of relay I2I, lower winding of the ringing trip relay I28, lower armature and back contact of this relay, contacts of relay I2I, over the ring conductor of the intercepting trunk to ground at 304 through the cold cathode gasfilled tube 305 over lead 306. This tube may be so arranged that it will break down on the positive half of the ringing current as soon as it is applied. Any well-known type may be arranged as shown with a control connection over condenser 301 to ground at 304. The control gap in this connection has a comparatively low breakdown voltage which produces suflicient ionization of the tube to assist in the breakdown of the main gap established through the connection over'the lead 306 to ground at 304. This breakdown connection over the main gap will then draw the peak current of the positive half of the ringing current. As soon as this occurs, tripping relay I28 will operate and close a locking circuit for itself from battery through its upper winding and its upper inner armature and front contact to ground at relay H6 and open the connection to the ringing source I26 for the ring conductor and. thus discontinue the ringing. The breakdown voltage and the sustaining voltage of these gaps of the tube 305 are still sufiiciently high to prevent a flow of the operating lower voltage direct current, applied on the ring conductor, from sustaining the ionization and cause current to fiow through the tube after the tripping relay is operated. That is, the battery connection through the lower winding of supervisory relay H5 over the ring conductor is of a voltage below the sustaining voltage of the tube 305 and consequently no current will flow from this battery through the tube and this relay will therefore not be operated falsely. A false operation of this relay would in this case cause the call to be charged on the calling subscribers meter or coin box, depending on the type of charging system employed.

On the operation of tripping relay I28 the connection for the tip and ring conductors of L the connector is extended from battery and ground through the windings of relay H5, contacts of relays I28 and I2I over the tip and ring conductors, left-hand windings of the repeating coil 3I0, and the windings of relay 3I2. The resistance of the lower winding of relay 3| 2 is sufiicien to prevent the operation of relay H5 at this time. As stated, on the operation of relay I 2i, relay 302 was operated. This relay in operating closes a circuit for the operation of relay 3! 5 from battery through the winding of this relay, contacts of relays 3I6 and 302 to ground. Relay 3I5 in operating closes a circuit for the operation of relay 320 located at the distant office in the intercepting trunk circuit. The circuit for relay 320 may be traced as follows: Battery and ground through the windings of relay 3I6, contacts of relay 3I5, right-hand windings of the repeating coil 3I0 over the tip and ring conductors and the left-hand windings of the repeating coil 32I, contacts of relay 323 through the windings of relay 320. Relay 320 in operating closes an obvious circuit for the signal lamp 322 which indicates to the intercepting operator that a call is waiting on this trunk. Relay 3 I 6 is marginal and does not operate in this circuit.

When the operator now answers this call by inserting plug 324 into the jack 300, a circuit is completed over the sleeve in the usual manner for the operation of relay 323 from battery over the sleeve through the winding of relay 323 to ground. This relay in operating opens the circuit for relay 320 which now releases and extinguishes lamp 322. A circuit is also closed for the operation of relay 326 from ground and battery through the windings of this relay, contacts of relays 32'! and 323 over the circuit traced through the windings of relay 3I6 to battery and ground. Battery and ground connections for these relays are such that both relays 326 and 3| 6 will operate. Relay 326 closes an obvious circuit for the operation of relay 329 which closes the tip and ring connection through the righthand windings of the repeating coil 32I towards the operators cord from battery through resistance 330 over the ring conductor and from ground through the winding of relay 332 over the 'tip conductor. Relay 3I6 in operating provides a locking circuit for itself to ground at relay '3I2. n the operation of relay 3I6, the circuit for relay 3I5 is opened and this relay in releasing closes a circuit from ground through the lower winding of relay 326, contacts of relays 321 and 323, the upper left-hand winding of repeating coil 32L the tip conductor, the upper right-hand winding of repeating coil 3I0, contacts of relay 3I5, resistance 335, upper windings of relays 336 and 331, contacts of relays 3I2 and 3I5, lower right-hand winding of repeating coil 3 I (I, the ring conductor, lower left-hand winding of repeating coil 32l, contacts of relays 323 and 321, upper winding of relay 326 to battery. The polarity of this connection from battery and ground through the upper winding of relay 336 is such that this relay will not operate asit is polarized. Relay 331, however, operates and relay 340 also operates over an obvious circuit. Relay 340 provides ground to hold relay 3I6 operated independent of relay 3 I 2 to hold the connection under the control of the intercepting operator. Relay 340 also provides -.an obvious circuit for the, operation of relay 303 which in turn opens the circuit for relay 302. Relay 302 opens the circuit for relay 3I5. The connection is now completed from the calling subscriber through the connection 0 and the intercepting trunk to the intercepting operator and conversation may proceed. Talking battery for the calling subscriber is applied through windings of relay H4 and the talking current is transmitted through the condensers I38 and I3I. The signaling battery through the left-hand windings of repeating coil 3H! is applied through the windings of relay H5. The conversation is repeated through repeating coils 3i!) and 32L In case the intercepted call was extended by way of a calling operator's position and the intercepting operator decides to recall the calling operator, she will apply intermittent battery on the tip conductor to cause the intermittent operation of relay 332. This relay in turn closes an obvious circuit for the operation of relay 321 which reverses the current over the tip and ring conductors of the intercepting trunk to cause the operation of the polarized relay 336. This relay inturn closes a connection for short-circuiting the lower high resistance winding of relay 3IZ for the operation of marginal relay H5. The circuit for these relays may be tra'ced'from battery through the lower winding of relay I I5 over the ring conductor, through contacts of relays 528 and I2I, left-hand lower winding of repeating coil 3H], contacts of relays 336 and 3%, upper winding of relay 1H2, upper left-hand winding of repeating coil 3H3, tip conductor and contacts of relays I26, E23 through the upper winding of relay M5 to ground. On the operation of relay M5, the battery and ground connection through the windings of relay IN!- is reversed over the tip and ring conductors to signal the calling operator by flashing impulses as is well known in the art. 1 i

If the calling party disconnects before the intercepting operator, relays H4 and I I6 release. This latter relay in turn releases relays I28 and I2! and a circuit for the release magnet I40 is closed from battery through the winding of this magnet, vertical off-normal contacts, contacts of relays I2I, H6 and H4 to ground and when the connector returns to normal the connection to the'trunk is opened at terminals I03. This causes the release of relay M2. The release of relay 3I2 removes the short circuit around the lower windings of relays 336 and 331 and resistance 338 thus decreasing the currentto relay 325 and causing it to release. This in turn releases relay 329 which gives a disconnect signal in the intercepting operators cord. When the operator disconnects by removing plug 32 from jack 3%, relay 323 is released, opening the talking circuit through the intercepting trunk. This in turn causesthe release of relays 326, 329, 331, 34G, 3H5

and 303. I

if, on the other hand, the called subscribers number had been that of theother party of the twoxparties originally connected to terminals I93 and I532 the brushes of the connector C would have landed on terminals 32. Under these conditions the ringing would be applied to the tip terminal of the connected intercepting trunk as the tip and ring terminals have been reversed as shown at 532. operate in the intercepting trunk to trip the ringing on the positive half of the ringing current in the same manner as tube 335 operated when the brushes of theconnector C were connected to terminals I95.

Under other conditions it may be desirable to trip during the negative as well as the positive portion of the ringing cycle with the ringing current incoming over either the tip or ring conductor. In such cases-the intercepting trunk would be changed to provide tubes in accordance with Fig. 5 connected between A-A' and BB so that no matteron which conductor the ringing current is received, it will be tripped immediately upon a'positive ornegative half of the ringing current. The wiring for the tubes would be as shown in Fig. 5, with the tube such as 323i connected in the same manner as tube 3% to respond on the positive half of ringing current applied on the tip conductor; with the tube 352 connected in the manner shown to the tip conductorto respond to the negative half of the ringing current applied on the tip conductor; with the tube 353 connected in the same manner as tube 365 to respond on the positive half of ringing current applied on the ring conductor, and with tube 35% connected in the manner shown to respond to the negative half of the ringing current applied to the ring conductor.

If the calling subscriber calls another disconnected subscriber in the same ofiice, the brushes of this connector may land on terminals such as I I2 to seize an intercepting trunk as shown in Fig. 2. In this case the relay M3 will operate over the sleeve to light lamp M4. When the intercepting operator sees this signal she inserts plug 351 of her intercepting cord circuit, Fig. 4, into jack Hit. It should be noted that in this case when ringing is applied from the source I2t,'it will be tripped by tube 358, bridged across the tip and ring conductors. The tube will ionize and break down to cause the flow of ringing current on either the positive or negative half of ringing current. Inserting plug 351 in jack lfifi'causes relays 359 and I41 to operate. Relay M1 opens the circuit through the winding of relay I 13 causing it to release and extinguish the line lamp I M. Relay 359 closes the ring conductor of the cord. Relay 3% is now operated from battery and ground from the connector. If the calling subscriber disconnects, relay 369 releases and the lamp 3'6I is lighted. The cord is also equipped with a flash- In this case the tube 353 will ing key 362 which varies the resistance of the supervisory bridge across the tip and ring conductors of the cord to give a flashing signal back toward the connector.

What is claimed is:

1. In a telephone system, a calling line, an operator's position, a trunk terminating in said position, switching means for establishing a connection from said calling line over said trunk to said position and for transmittingringing current over said trunk, and means controlled by the operator at said position and including a cold cathode tube for discontinuing said transmission of ringing current.

2. In a telephone system, a calling subscribers line, a trunk line, switching means including a connector switch for establishing a connection from said calling subscribers line to said trunk and for transmitting ringing current thereto, and means including cold cathode tubes in said trunk circuit and a relay in said connector responsive to the flow of ringing current for discontinuing the transmission of ringing current and for establishing a talking circuit over the trunk circuit from the subscribers line.

3. In a telephone system, a calling subscribers line, sets of tip, ring and sleeve terminals, switching means for establishing connections from a calling subscribers line through said switching means to said terminal sets, means associated with said terminal sets and said switching means for transmitting ringing current over the tip terminals when certain terminal sets are connected with and over the ring terminals when certain other terminal sets are connected with, trunk circuits each connected in multiple to the terminals of two sets, and means associated with the switching means and associated with each trunk circuit and including cold cathode tubes for discontinuing the transmission of ringing current regardless of the set of terminals with which the switching means is connected.

4. In a telephone system, a calling line, a trunk line, means for establishing a connection between said lines, a source of ringing current, a relay, a gas-filled cold cathode tube, a circuit including said source and said relay, means for closing said circuit through said tube to ground when said connection is established to transmit ringing current from said source through said tube to operate said relay, and means responsive to the operation of said relay for discontinuing said transmission of ringing current.

5. In a telephone system, a calling circuit, a trunk line, a connector switch, means for establishing a connection from said calling circuit to said trunk line over said connector switch, a source of ringing current associated with said connector switch, a relay associated with said connector switch, a gas-filled cold cathode tube associated with said trunk line, a circuit extending from said source through said relay and through the elements of said tube to ground, means for closing said circuit operative when said connection is established to transmit ringing current from said source over said circuit to operate said relay, and means responsive to the operation of said relay for opening said circuit toidiscontinue the transmission of said ringing current. i r

6. In a telephone system, a calling circuit, a trunkline, a connector switch, means for establishing a connection from said calling circuit to said trunk line over said connector switch, a source of ringing current associated with said calling circuit, a relay associated with said calling circuit, a gas-filled cold cathode tube associated with said trunk line, a circuit extending from said source through said relay and through the elements of said tube to ground, means for closing said circuit operative when said connection is established to transmit ringing current from said source over said circuit to operate said relay, means responsive to the operation of said relay for opening said circuit to discontinue the transmission of said ringing current, and means responsive on the operation of said relay for locking it in operated position.

'7. In a telephone system, a calling circuit, two sets of terminals each comprising a tip, a ring and a sleeve terminal, switching means for establishing connections from said calling circuit through said switching means to any one of said terminal sets, means associated with said switching means for transmitting ringing current over the tip terminal when one set of terminals are connected with and over the ring terminal when the other set of terminals are connected with, a trunk circuit connected in multiple to the terminals of said sets, cold cathode tubes associated with said trunk circuit, and circuit means operative through the elements of said tubes for discontinuing the transmission of ringing current regardless of the set of terminals with which theswitching means is connected.

8. In a telephone system, a calling circuit, sets of terminals .each comprising a tip, a ring and a sleeve terminal, switching means for establishing connections from said calling circuit throu'ghsaid switching means to any one of said terminal sets. means associated with said switching means for transmitting ringing current over the tip terminal when certain sets of terminals are connected and over the ring terminal when certain other sets of terminals are connected, trunk circuits each connected in multiple to the terminals of two sets, cold cathode tubes associated with each trunk circuit, and circuit means including the elements of a tube in a trunk circuit operative when a connection has been established from the switching means to said trunk circuit over a set of terminals for discontinuing the transmission of ringing current regardless of whether the ringing current is transmitted over a tip or a ring terminal.

9. In a telephone system a calling line, a trunk line, means for establishing a connection from said calling line to said trunk line, a source of ringing current, means for connecting said source to said trunk line, a space discharge tube, an operating circuit for said tube including the conductors of said trunk line and said source of ringing current, and means in said operating circuit responsive to the flow of ringing current over said operating circuit and through said tube for disconnecting said source from said trunk line.

JOHN DAVIDSON, JR. 

